Properties of Solutions and Rheology in Pharmacy

Ideal Solutions

Obey Raoult's law with no change in interactions.

Real Solutions

Do not obey Raoult's law; interactions vary.

Concentration

Amount of solute per unit solvent.

Activity

Effective concentration considering non-ideal behavior.

Osmolality

Moles of solute per kg solvent.

Osmolarity

Moles of solute per liter solution.

Water Activity (aw)

Measure of water availability in solutions.

Colligative Properties

Properties dependent on particle number in solution.

Tonicity

Effect of solution on cell volume.

Isotonic Solution

Same osmotic pressure as body fluids.

Hypertonic Solution

Higher osmotic pressure; causes cell shrinkage.

Hypotonic Solution

Lower osmotic pressure; causes cell swelling.

NaCl Equivalency

0.9% NaCl is isotonic solution.

Freezing Point Depression

Decrease in freezing point due to solutes.

Isotonic Volume Method

Calculates volume for isotonic drug solution.

White-Vincent Method

Calculates water volume for isotonicity.

Viscosity

Internal resistance to flow in liquids.

Newtonian Flow

Constant viscosity independent of shear stress.

Plastic Flow

Constant viscosity above yield stress.

Pseudoplastic Flow

Viscosity decreases with increased shear.

Dilatant Flow

Viscosity increases with shear stress.

Thixotropic Flow

Viscosity decreases over time under stress.

Methylcellulose (MC)

Nonionic polymer used to increase viscosity.

Carboxymethylcellulose Sodium (NaCMC)

Ionic polymer that thickens aqueous solutions.

Bentonite Magma

Thixotropic agent used in liquid formulations.

Xanthan Gum

Thickening agent that enhances viscosity.

Carbomer

Polymer that increases viscosity in formulations.

Syrup NF

Concentrated sucrose solution with self-preserving properties.

Osmotic Pressure

Pressure required to prevent solvent flow.

Viscosity-Inducing Agents

Substances that increase liquid viscosity.